Modeled urea distribution volume and mortality in the HEMO study

Summary Background and objectives In the Hemodialysis (HEMO) Study, observed small decreases in achieved equilibrated Kt/V_urea were noncausally associated with markedly increased mortality. Here we examine the association of mortality with modeled volume (V_m), the denominator of equilibrated Kt/V_urea. Design, setting, participants, & measurements Parameters derived from modeled urea kinetics (including V_m) and blood pressure (BP) were obtained monthly in 1846 patients. Case mix-adjusted time-dependent Cox regressions were used to relate the relative mortality hazard at each time point to V_m and to the change in V_m over the preceding 6 months. Mixed effects models were used to relate V_m to changes in intradialytic systolic BP and to other factors at each follow-up visit. Results Mortality was associated with V_m and change in V_m over the preceding 6 months. The association between change in V_m and mortality was independent of vascular access complications. In contrast, mortality was inversely associated with V calculated from anthropometric measurements (Vant). In case mix-adjusted analysis using V_m as a time-dependent covariate, the association of mortality with V_m strengthened after statistical adjustment for Vant. After adjustment for Vant, higher V_m was associated with slightly smaller reductions in intradialytic systolic BP and with risk factors for mortality including recent hospitalization and reductions in serum albumin concentration and body weight. Conclusions An increase in V_m is a marker for illness and mortality risk in hemodialysis patients. & copy 2011 by the American Society of Nephrology.